Amplifiers, particularly those employed in modern wireless communication networks, may have a variety of possible modes of operation. The optimum mode of operation depends upon the format of data transmission or modulation scheme and the frequency of transmission. Amplifier design variables such as transistor sizes, supply voltages, bias points, and impedances for the source and load are chosen to insure optimized efficiency, linearity, and gain control while meeting the specifications of a given transmission scheme. Different modulation schemes may place dramatically different requirements on the amplifier, leading to significant differences in ideal values for these variables.
In a typical amplifier most, if not all, of these variables are fixed in the design, meaning that the amplifier is suitable for only one mode of transmission. As an example, and not by way of limitation, it is desirable for the manufacturers of wireless handsets to utilize the same power amplifier for transmission of both EDGE (Enhanced Data rates for Global Evolution) and GSM (Global System for Mobile Communications) modulated signals for data and voice, respectively. However, EDGE requires a very linear amplifier for signal integrity, while GSM operates most efficiently in a highly saturated amplifier.
Thus, there is a strong need in the industry for an improved amplifier system and method capable of improved amplifier efficiency, linearity, and gain control for both linear and saturated modes of operation.